Control circuit for signal seeking tuner



E. F. ANDREWS CONTROL CIRCUIT FOR SIGNAL SEEKING TUNER sept. 15, 1959 voriginal Filled Nov. 15, 195o 2 Sheets-Sheet 1 j 7 wwf/Zay Jomhzov m l SEmzmw CSQN -Awww JOM PZC-v mZOP Sept. 15, 1959 E. F. ANDREWS 2,904,676

CONTROL CIRCUIT FOR SIGNAL SEEKING TUNER Original Filed Nov. 13, 1950 2 Sheets-Sheet 2 RECE IVER COMPONENTS gv/wezf/fm" f 7 .50u/#RD i?. ANDRews f@ @4 @my-fe gy nited States Patent O dward F. Andrews, Belleair Beach, lila., assignor, by rnesne assignments, to General Motors Corporation,

Detroit, Mich., a corporation of Delaware Original application November 13, 1950, Serial No. '195,16'1, now Patent No. 2,773,193, dated December 4, 1956. Divided and this application August 20, 1956, Serial No. 605,110

l 1 Claim. (Cl. Z50-20) This invention relates to signal tuned radio apparatus. Signal tuned radio receivers require no manual presetting to tune in progressively all transmitted signals of suflicient strength Within the frequency tuning range of the receiver. Signal tuned radio apparatus has broad utilityy and is applicable to home receivers and other radio apparatus as well as automobile receivers and other receivers which are subject to 'frequent changes of geographical position. Y

Signal tuned receivers have also been known in the art as stop-on-signal, stop-on-carrier, or signal seeking receivers. Signal ltuned apparatus of this general type has been described and claimed in other patents, such as those of E. F. Andrews Patent No. 2,493,741, issued Jan. 10, 1950, and O. Gierwiatowski Patent No. 2,494,235, issued Jan. l0, 1950, and E. F. Andrews Patent No. 2,541,018, issued Feb. 13, 1951. The present invention is applicable generally to resonant responsive electronic apparatus, but more specifically it constitutes an improvement on certain features of the signal tuned radio apparatus described in the above mentioned patents. This application is a division of Serial No. 195,161, filed Nov. 13, 1950,now Patent No. 2,773,193, dated December 4, 1956. j

It is one of the objects of this invention to provide certain advantages over and improvements upon the structures shown in the patents above referred' to. The solenoid, limit switch, and other parts associated with charging the tuner operating spring by electrical' power are items of considerable cost. Occasionally they may also fail to operate properly in service. For instance, if the voltage of the car battery is sufficiently reduced .and the limit switch operates to energize the solenoid, the force produced by the solenoid at this lowy voltage may be insuiiicient to effect operation and instead ofthe limit switch interrupting the current it remains closed and the solenoid continues to draw a considerable current which could cause overheating and/or still 'further discharge of the storage battery. Although safeguards can be provided, they add still further to the cost.

According to one of the features of this invention, economy and reliability can both be enhanced by providing means for recharging the tuning drive spring manually at the end of each frequency band traverse or at any intermediate position. Manual recharging requires Vlittle elfo-rt and is necessary only infrequently because ordinarily from ten to fifty stations can be tuned before the spring must again be charged. Recharging may be performed by a further movement of the same control member which starts the tuner to tune in another station. This arrangement has the further advantage that by an appropriate movement of the control member the tuner can be moved in the spring charging direction any amount desired and this movement can be initiated while the tuner is in any intermediate position between the discharged and. charged positions of the spring. With the structure shown in the above patents the spring charging operation is not initiated by the solenoid until the high frequency or spring-discharged end of the scale has been 'Patentes sept. 15, 1959 reached, and then the tuner is moved all the way to the low frequency or spring-charged end. During charging of the springs no means is provided for stopping at any intermediate position adjacent a desired station as can be done by the proper manual operation o-f the manual tuning and recharging control of this invention,

Likewise, with the solenoid recharged tuner, if the starting switch is inadvertently operated the tuner must go all the way to the high frequency end, all the way ba'c'k to the low frequency end by the action of the solenoid, and then from the low frequency end toward the high frequency end to return to the desired station. With the manual recharging control, the control may be moved a very small distance sufficient to pass to the low frequency side of the desired station. If the control is then released the desired station will be immediately tuned in. If the operator knows the position of any desired station `on the visual tuning scale, he can immediately tune it in in a single quick operation by this method. Experience has shown that this is often a very worth-while advantage, particularly when many stations of suiiicient strength to operate the tuner are present across the band.

One object of the present invention therefore is to provide an improved signal tuned or stop-on-signal radio apparatus.

Another object is to provide an improved signal tuned radio receiver.

A 'further object is to provide a new and improved signal tuned radio apparatus including variable tuning means, potential energy storage means for varying the tuning means, means for terminating variation of the tuning means by the potential energy storage means in response to a signal tuned by the tuning means, and manually operated means for recharging the energy storage means and for restarting the tuning means to tune in a different signal. The energy storage means is preferably a stressed spring means, but may be of some other suitable type such as piston or bellows s-ubject to fluid pressure or any elevated weight.

A further object is to provide a compact, readily producible, signal tuned device in which the tuning mechaj nism'is driven in one direction by a spring or other suitable energy storage means, and in which the energy storage means is recharged and the tuning mechanism simultaneously moved in the opposite direction by manually moving a charging and positioning member.

A- further objectis to provide a signal tuned device in which a small movement of a member causes the energy storage means to move the tuning means to tune in a station and a second small movement causes the tuning in of another station in the same Way, while a large movement of the same member causes the energy storage means to be recharged.

A further object is to provide a member manually rotatable; in one direction to charge yan energy storage means for varying the tuning means, and in which ashort axial movement of an associated member causes the energy storage means to move the tuning means until the tuning means is signal tuned to another station, if the signal of a station is present and of required strength.

It is a further object to provide a signal tuned device with a member in which a short movement of the member etects the signal tuning of successive stations by a resilient driving means, and in which a larger motion of the member effects the recharging of said resilient means, and inwhich two-directional manual tuning, as differentiated from signal tuning, is accomplished oy motions of the tuningmember in opposite directions.

It is a further object to provide a signal tuned device, for instance |any of those described inl previous objects, with' means by which the resilient means for varying. the tuner may be rechargedv to any desired degree by a smaller:

or larger manual movement of a tuning member, and in which the tuning means is moved in one direction a smaller or a larger vdistance corresponding to the movement of the tuning member.

It is 'a further object to provide a signal tuned mecha-V nism of the type previously described in which the tuner can be moved a desired distance in one direction and the tuner drive mechanism recharged not only when the tuner drive mechanism is completely discharged, but also at any intermediate position between charge and discharge.

Further objects, advantages and features of this invention will become |apparent from the following description of several illustrative embodiments taken with the drawings in which:

Figure l is a diagrammatic view of an illustrative signal tuned radio receiver constructed in accordance with the invention;

Figure 2 is a perspective view showing the external appearance of the receiver;

Figure 3 is a diagrammatic side elevational sectional view illustrating -a modified embodiment;

Figure 4 is a fragmentary front elevational view illustrating the external appearance of the embodiment of Figure 3, a portion of the external wall of the receiver being broken away to illustrate mechanical details;

`Figure 5 is a fragmentary elevational sectional view illustrating another modified embodiment;

Figure 6Vis a fragmentary sectional View taken on line 6-6 of Figure 5; and

Figure 7 is a fragmentary elevational sectional view illustrating a modification of the embodiment of Figures 3 and 4.

Certain features of the yapparatus disclosed in this application are not a part of this invention and will be disclosed and claimed in other copending applications.v

The signal tuned radio receiver illustrated in Fig. l has many of the components of the usual supcrheterodyne receiver. It has `a radio frequency amplifier 10 with an input to which an antenna l2 may be connected. A Superheterodyne converter stage 14 is coupled to the output of the R.F. amplifier `10. The converter 14 may include a rst detector, an oscillator, and an I F.V input transformer for coupling the output of the rst detector to an intermediate frequency amplifier tube `16.

The output of the LF. tube 16 is coupled to a diodetriode tube 18 which functions as the detector for listenspring 50 is positioned around the pushrod to urge it outwardly. A C-washer or abutment 52, mounted on the pushrod 46, is engageable with the front of the crosspiece 40 when the pushrod is pushed inwardly.

The rack meshes with a pinion 54. A coil spring 56 produces a clockwise torque on the pinion' so asv to urge the rack outwardly.

A spring pressed pawl 58 pivoted on a gear wheel 60 engages the pinion for transmitting clockwise rotation of the pinion to the gear 60. The gear 60 meshes with a pinion 62 fixed to a. second gear wheel 64 which meshes with a pinion 66. The pinion 66 is fixed to a brake disc armature 72 and the winding 80 operating to release tracted position by residual magnetism, once it has been` 'an automobile battery. The battery is utilized to ener-` the armature. frame 84. The magnetic circuit formed lby the core 82, the frame 84 and the armature 72 has considerable retentivity so that the armature may be retained in atmoved to attracted or closed position by energization of the -winding 78. Energization of the winding 80 releases the armature by bucking the residual magnetism.

The receiver is powered by a battery 86 which may be gize the winding 78 for attracting the armature 72 to commence'tuning. The attracting winding 78 of the relay 70 is connected across the battery 86 through a starting switch 87 comprising a pair of contact springs 88 and 90. The contacts 88 and 90 are normally held ing and as the actuating voltage rectifier for signal tun- 21 to a second audio amplifier tube 22 having an output l.

transformer 24 in its plate circuit. The tubes 20 and 22 function as amplifiers during both listening and signal tuning. A speaker 26 is provided for listening.

The receiver includes a radio frequency tuning inductance 28, a first detector tuning inductance 30, and an oscillator tuning inductance 32 which are connected with the corresponding portions of the circuit by means of pairs of leads X, Y and Z, respectively. F or convenience and clarity only the end portions of the leads are shown. The inductance coils 28, 30 and 32 are mounted with their axes parallel. The coils are tunable by means of cores or slugs 34, 36 and 38 which are movable in an axial direction.

The tuning cores 34, 36 and 38 are mounted on Va crosspiece 40 which is supported by a rack member 42. The rack 42 is slidably mounted on a supporting rod 44. The crosspiece is slidably guided by a pushrod or control plunger 46 to restrain the rack from rotation on the supporting rod 44 and to maintain alignment between Ythe cores 34, 36 and 38 and the coils 28, 30 and 32. A knob 48 is provided on the front end of the pushrod 46 for manually pushing the rod inwardly, and a helical return open by engagement of the washer 52 on the pushrod 46 with a spring member 92 mechanically connected with the contact spring 88 but electrically insulated therefrom. When the knob 48 on the pushrod is pushed inwardly, the washer 52 is disengaged from the spring member 92 and the spring member closes the contacts 88 and 90.V The contacts are shunted by a bleeder resistor 94 which permits a small current to ow through the attracting winding 78 when the contacts are open to augment the residual magnetism and to provide an 'adjustment of the force tending to hold the armature in attracted or closed position. If the bleeder current or the retentivity of the magnetic material is suitably increased, the relay armature may be moved to closed position by a directly applied manual movement if desired. Under these circum. stances the closing winding and the starting switch would beeliminated.

Energy for tuning the receiver is stored in the coil spring 56 by manually moving the knob 48 on the pushrod 46 inwardly. This Vproduces inward movement of the rack 42 and rotates the pinion 54 counterclockwise to tension thecoil spring. The pawl 58 ratchets over the teeth of the pinion so that the gear wheel 6i) does not have to rotate while the spring is being charged.

When the spring 56 has been charged, tuning may be commenced `by tapping the knob 48 to close the contacts 88 and 90 momentarily. When the contacts are closed, the winding 78 is energized to attract the armature 72 out of engagement with the stopping member or brake disc 68. After the contacts 88 yand 90 are opened, the armature is held in attracted position by residual magnetism, magnetism produced by bleeder current through the resistor 94, or both.

. When a signal is tuned in, an impulse from the output transformer 24 is impressed upon the releasing winding The relay has a core 82 mounted in aV acoger S armature is released, it is again engaged with the brake disc 68 by the spring 74, and tuning is stopped on the signal. v

The relay 70 operates switch means 99 including a number of movable contacts. A movable contact 100 is movable between staitionary contacts 102 and 104 for connecting la secondary winding 105 of the output transformer 24 with the speaker 26 when the armature 72 is released and with the releasing winding 80 when the armature 72 is attracted. Thus the output transformer is connected with the speaker for `listening and with the releasing winding for tuning.

The means for producing an impulse for stopping the tuning of the receiver on a signal will now be described.

Plate voltage for the receiver is applied by a vibrator B supply 106 having two B+ output conductors 108 and 110. The B supply 106 is connected with the battery 86 through a switch 112 and an interference filter comprising a series inductance 114 and a pair of shunt capacitors 116 and 118.

An LF. output transformer 120y couples the intermediate frequency amplifier pentode 16 `with the detector tube 18. The transformer 120 has la primary winding 122 connected between the anode of the pentode 16 and the B supply conductor 108. The primary 122 is shunted by a capacitor 124 to form a tuned circuit.

A secondary tuned circuit comprising a secondary winding 126 in parallel with a capacitor 128 is coupled with the primary winding 122. One end of the tuned secondary winding 126 is connected to the anode 130 of the diode section of the tube 18. The other end of the secondary winding 126 is connected with the cathode o-f the diode-triode tube 18 through a series circuit including an intermediate frequency filtering resistor 132, a volume control and diode load resistor 134, and a cathode load resistor 136. Two intermediate frequency bypass capacitors 137 are connected respectively between the ends of the filtering resistor 132 and ground.

The LF. output transformer 120 has an untuned secondary winding 138 which is closely coupled to the primary winding 122. The windings 122 and 138 may constitute a single winding of multiple strandy Litz wire, some of the strands being used for the primary winding 122 and others being used for secondary winding 138. A ferromagnetic core 143 axially movable within the winding 122 may be provided to tune the primary circuit, comprising the winding 122 and capacitor 124, to resonance. The secondary winding 126 may be carried in axially spaced relation to the winding 122 and 138. A second ferromagnetic core 145 may be provided to tune the secondary circuit, comprising winding 126 and capacitor 128, to resonance. The coupling between the primary winding 122 and the secondary winding 126 may be changed, for instance, by adjusting the axial spacing of fthe two windings.

One end of the untuned secondary 138 is connected with the grid of the diode-triode tube 18, and the other end is connected to ground through a resistor 139 shunted by a bypass capacitor 141. The triode section of the tube 18 is connected `as an infinite impedance rectifier. The triode anode 140 of the tube 18 is connected directly with the B supply conductor 108 and is bypassed to ground by a capacitor 142. The resistor 136 serves as a load resistance for the triode section of the tube 18. This resistor also provides resistance coupling between the triode and diode circuits of the tube 18. The cathode is bypassed to ground through an intermediate frequency bypass capacitor 144. In order to furnish cathode bias voltages the conductor 146 wh-ich connects the volume control resistor 134 and the cathode load resistor 136 is connected with the B supply conductor 108 through a resistor 148.

A movable contact 152 operated by the relay armature 72 engages a stationary contact 154 to short out the cathode load resistor 136 when the armature is in its listening position in engagement with the brake disc 68. When 6 the armature is in its tuning position the movable contact 152 engages a stationary contact 156 tto connect the conductor 146 with the junction 158 of the secondary winding 138 and the resistor 139 through a resistor 160. When the relay armature 72 is in listening position there is a large positive voltage on the cathode of the tube 18 supplied from lead 108 through the resistor 148, while the grid, which is connected to ground through resistor 139, is maintained substantially at ground potential.

When the relay armature is in the tuning position the cathode load resistor 136 is in the circuit. A delay bias for the triode section of the tube 18 is developed by the Voltage drop across the resistor 160, which now establishes bias on the grid relative to the cathode by raising the voltage at junction 158 above ground. The current fiowing from the B supply conductor 108 through the resistor 168 provides delay bias for the triode restraining voltage rectifier section of the tube 18. This prevents the application of restraining voltage until the signal has reached listenable strength.

The grid of the first audio amplifier triode' section of the tube 20 is shunted to the cathode by a resistor 162. The grid is connected through acoupling'capacitor 164 to a movable contact 166 operated by the relay armature '72. When the 'relay'armature' `is in listening position, "the movable contact 166 engages a stationary contact 168 connected with the slider 169 of the volume control 134. When the relay armature 72 is in the tuning position, the movable contact 166 engages a stationary contact 170 connected with the diode plate end of the volume control resistor 134 by an interference filtering resistor 172 and shunted to ground by an interference bypass capacitor 174. Thus dierent adjustments of the volume control have no effect during tuning.

The tube 22 isconnected as a power amplifier. The output transformer 24 has `a primary winding 176 which connects the anode of the tube 22'with the B supply conductor 110. 1

A series circuit comprising a tone control capacitor 17 8- and a variable tone control resistor connected between the grid of the tube 22 and ground.

The tube 20 has a diode anode 182 which is coupled to the untuned secondary 138 through an intermediate frequency coupling capacitor 184. The anode'182 is connected to ground through a load resistor 186 and to an automatic volume control line conductor 188 through an automatic volume control filtering resistor 190. A bypass capacitor 192 connects the AVC line 188 to ground. The AVC line is connected with the R.F. amplifier 10, the first detector forming a part of the converter stage 14, and through the I.F. input transformer with the grid of the LF. pentode 16.

It is advantageous for both listening and tuning to prevent operation of the AVC on weak signals. This may be accomplished by providing a delay bias to prevent operation of the AVC rectifier at low signal inputs. By this means the full sensitivity of the receiver is 'available at `low signal inputs Nvhile at high signal inputs the AVC operates in the usual manner to hold `the output at a substantially constant level. f

A cathode resistor 194 is connected between the cathode of the diode-triode tube 20 and ground. The cathode is connected through a voltage dividing resistor 196 shunted by a capacitor 198 to the conductor 146 and thence through the resistor 148 to the B supply conductor 108. The voltage drop across the resistor 194 provides an AVC delay bias.

The cathodes of the radio frequency amplifier tube and the first detector tube are brought out by conductors 200 and 202 which are connected to ground through a variable sensitivity control resistor 204 shunted by a bypass capacitor 206. The conductors 200` and 202 are connected with a stationary contact 208 on the relay 70 which is shorted to ground by a movable contact 210 when the relay armature 72 is in listening position so that the sensitivity control is effective only during tuning,

Aaso/terre In the operation of the receiver, the spring 56 may be charged initially by manually pressing the knob 48 on the pushrod 46 inwardly. The rack 42 is thereby moved reawardly and the cores 34, 36 and 38 are moved into their respective coils 28, 30 and 32. Th-is tunes the receiver to the low frequency end of the frequency spectrum. The knob 48 is promptly released after it is moved inwardly. The attracting winding 78 closes the relay when the inward motion of the pushrod 46 permits the spring member 92 to close the contacts 88 and 90. Thus the relay armature 72 is attracted and the brake disc is released so that the spring motor 56 can now move the tuner. 'Ihe contacts 88 and 90 are opened when the pushrod is released, since the return spring 50 overcomes the force of the spring member 92.

This reduces the current through the coil 78 but the armature 72 is retained in attracted position by residual magnetism and/or by the magnetic eld produced by the current through the bleeder resistor 94 passing through the attracting winding 78.

The spring 56 rotates the pinion 54 and thereby moves the rack 42 forwardly. Since the cores 34, 36 and 38 are moved out of their respective coils the receiver is tuned toward the high frequency end of the tuning range.

Returning now to the signal tuning circuits, as stated above, the coupling between the primary 122 and the secondary 126 is initially factory adjusted by moving one of the coils to increase or decrease the 'axial distance between them. A degree of coupling between these coils which gives very good results may be secured in the following manner.

. First, the grid-cathode bias of the tube 18 should be selected so that the plate current of the tube is at cutoff with zero signal input so that the tube current will not affect the bias at zero signal. Then with a signal of moderate strength applied to the grid of the tube 16, the coupling of the coils is adjusted so that there is an appreciable voltage output from the diode section of the tube 18, measured, for instance, across the Volume control resistor 134. The coupling is then reduced until this voltage substantially disappears. This means that the restraining voltage developed across the resistor 136 and applied to the plate 130 is substantially equal to the voltage applied to the plate 130 from the coil 126.

Next, the bias between the cathode and the grid of the tube 18 is varied by changing the value of resistance 160 to provide an increase of three or four volts to provide a delay bias. With this additional bias applied to the restraining voltage triode rectifier, an actuating voltage will appear across the resistor 134 as long as a signal is applied, for instance, to the grid of the tube 16, as previously described. The voltage across the'resistor 134 will increase as the applied signal increases until the applied signal equals the delay bias, after 'which there will be no further substantial voltage increase. Since the voltage output does not increase further with strong signals the width of the signal in terms of frequency does not undergo a further increase and both strong and weak signals are tuned closely to the center I F. frequency.

The tuning response characteristic of the untuned secondary winding 138 is like that of the .primary 122 and is somewhat broader than the response characteristics of the other secondary tuned circuit comprising the Winding 126 and the capacitor 128. The response of the untuned circuit should not be narrower than that of the tuned circuit. In normal operation of the system after it has been initially set, as a signal is approached, a substantial signal voltage first tends to develop across the secondary 138 and rises gradually in magnitude along a broad re- The signal voltage across the secondary 138 is applied to the grid of the triode section of the tube 18T and produces a positive rectified output voltage across the cathode load resistor 136 when the signal exceeds the vdelay bias supplied by the Voltage drop across the resistor 160. Y

A`As the receiver is tuned more closely to the signal by the spring 56, an additional voltage begins to develop across the more sharply tuned secondary winding 126t Since the load resistor 136 is in series with the circuit connecting the diode plate to the cathode of the` tube 18, the rectified signal voltage across the resistor 136, due to Ithe triode infinite impedance rectifier, biases the cathode positively with respect to the diode anode 130 and` thereby restrains rectification by the diode 130,- cathode until the voltage across the tuned secondary 126 exceeds the bias, due -to the triode rectifier, across the resistor 136. The drop across the resistor 160, caused by current from the B supply, provides a delay bias which holds the grid a few volts negative relative to the cathode of the triode section of the tube 18. This fixed delay bias prevents rectification in the triode rectifier and thus delays theV buildup of the variable positive restrain-ing voltage until the signal across the secondary 138 exceeds the delay bias. The variable positive restraining voltage retarded by the delay bias across resistor prevents strong stations from producing a tuning indexing or stopping signal much higher and wider than the rweaker stations, and togetherl they provide relatively uniform indexing response of the actuating circuit to signals of varying magnitude.

When the amplitude of the incoming signal increases to a point where the diode section of the tube 18 begins to conduct, a signal impulse is transmitted to the grid of the first audio triode section of the tube 20 through the static filtering resistor 172, the contacts and 166, and the coupling capacitor 164. This signal impulse is amplified through tubes 20 and 22, and applied to transformer 24. The secondary 105 of the transformer is at this time connected in series with relay coil 30 Which is energized to overcome the residual magnetism of the relay, releasing armature 72 to stop the tuner. It will be seen that, although the signal from the diode section of the tube 18 follows the path through the static filter during tuning and through the volume control resistor 134 and slider 169 during listening, as determined by the position of the switch contact 166, the tuning and the listening signals nevertheless come from the same diode and also from the same tuned circuit consisting of the inductance 126 and capacitor 128. As a result, the last tuned circuit that establishesthe frequency for signal tuning is also the last tuned circuit which establishes the frequency of the signal during listening. Although during tuning the width of the response of this tuned lcircuit is narrowed, particularly to strong signals, the center frequency is the same as during listening. This eliminates possible error in tuning which might occur if a different tuned circuit were employed for tuning and listening, Where one circuit could get out of tune with respect to the other.

As mentioned, the impulse amplified by the first audio triode 20 and the power amplifier tube 22 is supplied to the relay releasing winding 80S by the secondary 105 of the output transformer 24. This impulse is of relatively low frequency and, therefore, it is desirable that theout'put transformer be of such construction as to provide effective power output at low frequencies. For similar reasons, the couplingcondenser 21 should also be of suicient capacity. A resistor and a capacitor 177 are provided to improve sensitivity and proper relay action. The secondary of the output transformer and the releasing winding 80 are polarized with respect to the attracting winding 78 so that the first signal impulse through the releasing Winding bucks or counteracts the residual magnetism and/ or the magnetism caused by the current in the attracting winding 78 through bleeder 94. If the impulse is of sufiicient strength, the relay armature 72 is released and tuning is discontinued by engagement of the armature with the brake disc or stopping member 68.

The lmagnitude of the holding current through the "tion of the tuning mechanism is not affected by the Setting of the volume control resistor 1.3.4.becausethe slider 169 of the volume control is disconnected during tuning, 'and the signal' output is taken through the interference filtering resistor .1 72. from the end of the volumeeontrol resistor connected with the diode anode'130. During tuning, the resistor 172 Vand the capacitor'174 provide additional iiltering to minimize the possibility f V,the

tunerb'eing stopped byfstatic o r -other interference. This ilter does notoappreciably aflecttheaudio response dur- -ing listening.

-Wlie'n the relay armature 72, hasbeen released to stop the' tuning.. the .movable relay, contacts Shift td. their. listen- .ig positions. lThe movable contact 2'10 shorts o ut'the sensitivity controlwresistjor l 2tk4so thatthe fullvsensitivity of the'receiyer Acontrolled by the AVC yis available ,for

listening.

' ,During llisteningnthevmovable contactlZ shorts out the cathode load resistor 1,36 toiprevent anysignal voltages from developing acrossthisiresistor, andto permit the full signal' voltage toidevelop acrossthe volume control 'resistorj134- "l'hetriodesectionpf thetubedS/is cut off by disconnecting the resistor .1640' from the positively charged conductor L1.46thus permittingthe grid of the triode section todrop to ground potential. ,Theconducltor 146 is at a positive potential high enoughtofeffectively preventreetiiication rin the trioderestraining voltage rec- ,tiierf with the strongest signal A input.

For listening, the movable contact .166 connects the input ofthe first audio tube .Zttotheslider 1,69foffthe volume control resistor so that the slider may be adjusted to varylthe volume.

IFiguie l2 illustrates theexternal appearance of v the receiver. The pushrod or control v plunger .46 lprotrndes through a panel v,211.- enelosing thefrontvofthereceiver.

A dial or scale 12112.havingy anindicator :214;is positioned l.iinmediately belowthe pushrod 46. .The volumefeontrol resister .ftand the battery Switch .1.1.2.may B Csllll.frolld ,by a knob ,Maand the tene.contrelfesstsrlll marte@ controlledby a ring ,2116. .The ,sensitivity ontrolmay'be ycontrolledby ,a knob Illffandthe receiver may be conditioned fof mannal or signal tuning by means of alever 219. The yreceiver may .tbe enclosed in a ,honsing .2,201

and may beadaptsd-,fof @Dating 0.11111@ dash Qf-.an .alltolmobile.

Many of ,the advantages Vof ythe l embodiment `of the .invention illustratedinfisurs 1 arldiha'v lssdyzbeen discussed. Rechargine thssprins 56m/righi@ theknb .on ,the Control plunger inwardly Navires little 1921.129211 effort since the spring need ,be strong enoughv only `to insure reliable starting. Recharging ofthe spring is necessary only after the entire tuning range Yhas .been traversed. This occurs infrequently since several sta- .tions spaced aerossthe tuningirangewill ordinarily have sluiiicient strength for signal "tuningvinrrnostilocalities.

If the station'whichis desired isinadvertently passedv durinssisnaltunine, by .citsnfally tapping the @Html knob, the knob may be pressed inwardly to"'1nove 4the tuning cores reversely ashort distance -just beyond the station ac cidentallypassed.'A y'Theamount thetuning cores 'armoved and the'amount'the spring is recharged are deter` ine'dby'the" extent'v'ovf the inward movementfof'the 'eontr'olknobL I'fthe tunin'gcores have been moved manally some'distance to the lowzfrequenc'y side of la-V desired station,` the station may be tined in by tapping" the'con'trbl knobrepe'atedly untilT the 'station is heardi The receiver v'driven direction.

:10 dial may be observed during this procedure if ,the station cannot. be identified by ear.

If'the location of the desired station onthe dial lis known, the station maybe tuned in quickly by pushingy the control knob inwardly to tune fthe receiver to a point slightly on the low'frequericy side of the desired station as indicated on the dial. .The desired station will then be signal tuned when the knob is released.

During signal tuning, the driving spring -56 continuously maintains a torque upon the pinion -54 andthereby takes up any slack in the gearing connecting the pinion with the stopping member 68. This feature'subs'tantially prevents any slack' in the gearing from causing inaccurate signal tuning. If desired, the apparatus of Figures l and 2 may be modified slightly so that the driving spring also takes up any slack which may exist between the rack `42 and the pinion 54. This may be d'one by providing a separate pinion meshing with the rack 42. The torsional driving spring `5'6 is then connected to this separate pinion which drives the rack during tuning, taking up the play between the pinion 54 and the rack .42. The rack maybe Vlengthened or otherwise modied for this purpose. A

straight tensionhelical spring may also ,be employed acting linearly on the rack. Such a spring should be extended a long distance'from zero tension position compared to the change in length that the spring undergoes in moving the rack from one end of its travel to the 'other'.

A modified form of the invention is illustratedv in Figures 3 and 4. yThe modification relates particularly to -the relay controlled spring operated mechanism for driving fthe tuning elements of the receiver. The other components ofthe receiver may be the same as in the embodiment 'of Figures l and 2. These components are indicated in Figure 3 by a box 350.

" The embodiment of 'Figure 3 includes the relay 70 as described above. The attracting winding 7S ofthe relay is energized'fromB supply terminals 352 of the receiver through a starting switch 354 having a pair of normally yspaced apart contact springs 356 and 3158.

The embodiment of Figure .3 includes the stopping member 'or brake disc 68, the pinion `66 and the wind vane' 69 'mounted on the shaft '226 as previously described.

The'pinion 66 meshes with a gear wheel 360 carrying afspring pressed pawl 362 which engages a pinion 364. The gear wheel 360 and pinion 364 are coaxial and independently rotatable. The pinion '364 meshes with a gear wheel 366 mounted on a hub 368 which is rotatable on a' shaft37t).` A spring '372, coiled around the hub 368, has its opposite ends secured to the gear wheel 366 and a statioharyipart of the tuning means .37.4. Thev shaft .370 is lthe control shaft of a variable gang condenser or other tuning means i374 forming a part of v the receiver." 'n

A control knob 376 supporting a radial indicator 3178 is fixed to the outerl endof the shaft'..370. As shown 'fin Figure' 4 'the indicatoris rotatable along a graduated dial aso. f

""""-The"knob 376is engageable with the gear wheel .365

by means of va pin 382 which'may be inserted into a single aperture 384 in the gear wheel. A spring 386 coiled aroundV the pin and compressed between theknob fand an abutment washer 338 urges the pin toward engage- -rentv'vith'the gear wheel 366. It maybe disengaged by sliding 'the pin manually outwardly, andthe pin may be retained'in this position'by rotating the pin until a radial nger '390 en'gages'a shoulder 392 on the knob. When thepin 382' is engaged with the aperture384 in the g'ear wheel 36.6, the lfinger 390 is Vpositioned in a slot 394.'

y Astopping pin 393 on the gear 366 and ya stationary abutment 395 which may be mounted on the tuning means 37A limit the Vrotation of V the gear .in thespring `the open switch position.

The starting switch 354 is operable by means of a push button 396 which may be supported at the centerv of the outer face of the yknob 376 by means of a plurality of rods 397 extending longitudinally through the knob. A ring 398 positioned around the shaft 370 is secured to the inner ends of the rods 397. When the push button 396 is pushed inwardly, the ring 398 engages the front contact spring 358 of the starting switch for closing the latter. The spring of the contact moves it normally into The push button may be mounted on the panel of the receiver rather than on the knob if desired.

In operating the embodiment of Figures 3 and 4 the driving spring 372 is charged by manually rotating the knob 376 in a clockwise direction. This rotates the pinion 364 in acounterclockwise direction. The pawl 362 is free to ratchet over the pinion so that the gear wheel 360 does not have to rotate. Consequently the armature 72 of the relay may remain in contact with the stopping member 368 during charging of the spring. In order to charge the spring the pin 382 must be engaged with the aperture '384 in the gear wheel 366.

Rotation of the knob 376 to charge the driving spring 372 also produces rotation of the tuning shaft 370 and thereby moves that tuning means '374 toward one end of its tuning range. The knob 376 may be rotated suliiciently to move the tuning means all the way to the end of its tuning range or only part way, as desired.

The change in the tension of the spring, produced by' charging the spring, is relatively small with respect to the initial tension on the spring. Consequently the torque exerted by the spring is relatively const-ant throughout the tuning range of the receiver.

When the driving spring 372 is charged, the push button 396 may be tapped to close the starting switch 354 momentarily. This energizes the attracting winding 78 of the relay and releases the relay armature 7'2 from the stopping member 68 to commence tuning, as previously described in connection with the embodiment of Figures 1 -and 2. During tuning the gear wheel 366 drives the pinion 364 in a lockwise direction so that the pawl 362 is carried along to produce rotation of the gear wheel 360, the `stopping member 68 and the wind vane 230.

As indicated, the releasing winding `80 may be connected with the receiver components indicated by the box 350 in the same manner as in the embodiment of Figures 1 and 2. T he relay 70 of the embodiment of Figure 3 operates the switch means `99 as previously described.

When a signal of sufhcient strength is tuned in, an impulse is impressed upon the releasing Winding '80 to release the relay armature 72 and stop the brake disc 68. With respect to stopping, the pawl 362 forms a positive driving connection between lthe pinion 364 and the gear 360 so that the stopping of the brake disc 68 stops the tuning accurately on the signal.

The driving spring 372 maintains a torque upon the gear Wheel 366 when the tuning is stopped on a signal so that any slack in the gear train is taken up.

When manual tuning is desired the pin 382 may be Withdrawn from the gear wheel 366 as previously described. Rotation of the knob 376 then produces rotation of the tuning shaft 370 without charging the spring 372 or rotating the wind vane or brake drum. When the pin 382 is withdrawn, the spring driven tuning mechanism is entirely disconnected from the tuning shaft 370 so that it offers no resistance to the rotation of the knob 376.

In the event that the relay armature 72 releases the stopping member 68 while the pin 382 is withdrawn, the engagement of the stopping pin 393, on the gear 366,

with the abutment 395 prevents complete unWinding ofl the spring 372 so that an initial tension is maintained on the spring. The gearY stops at a position corresponding to one end of the tuning range of the receiver.

Other features of the construction and operation of the embodiment of Figure 3 which have not tbeen speciIc--;

by rotating a shaft 401. A gear wheel 400` is mounted on a hub 402 which is fixed to the shaft 401. The gear wheel 400 may replace the gear 60 and mesh with the pinion 62 illustrated in Figure 1.

A knob 404 is rotatable on the outer end of the shaft 401. A spring 406, coiled around the shaft 401, has its opposite ends attached to the gear wheel 400 and the knob 404. The knob is slidable inwardly against the resilient resistance of the spring 406 to engage the contact spring 358 and thereby close the starting switch 354. vThe gear wheel 400 may mesh with a gear wheel 408 for operating an indicator of any suitable type. l

A ratchet wheel 414 is fixed to the knob 404. A relatively long chisel pointed pawl 416 is movable into engagement with the ratchet wheel 414 for selectively restraining either clockwise or counterclockwise rotation of the knob. The pawl remains in engagement with ratchet wheel 414 due to gravity. The pawl is mounted on one end of a shaft 418 rotatably supported in a bushing 410 carried on a panel plate 412, the pawl being positioned on the front side of the panel plate. A pin 420, fixed to the pawl 416, is provided for moving the pawl manually into its various positions. An eccentric cam 422 is xed to the other end of the shaft 418. This cam is provided with a notch 424.

A bracket 426 carried by the panel member 412 may be provided to support a rod member 428 for axial movement. A washer 430 is fixed to the rod 428. A compression spring 432 operates between one bracket member 434 and the Washer 430 to urge the rounded end of the rod 428 toward the surface of the cam 422. A knob 436 is carried on the end of the shaft 401 and may be secured to the shaft by a set screw 438.

For manual operation the pawl 416 is disengaged from the ratchet wheel 414 and is moved into a vertical' position as viewed in Figure 6. Movement of the pawl 416 rotates the cam 422 which engages the end of the rod 428 and moves it upwardly against the force of the compression spring 432. When the pawl 416 reaches a vertical position the end of the rod 428 drops into the notch 424 in the cam 422. The force of the spring 432 holds the end of the rod 428 in engagement with the notch 424 in the cam 416 to retain the cam and the pawl 416 in position. The rod 428 in Figure 5 operates to disengage the armature 72 of the relay 70 from the brake member 68 to permit free rotation of the gear train. However, the armature 72 is not moved enough to change the position of the switching means 99. After the pawl 416 is placed in the position as described above, manual tuning may be accomplished fby rotating the knob 436 in either direction to tune in signals. Rotation of the tuning knob operates the tuning means 399, the indicator gear wheel 408 and the entire gear train which is driven by the gear wheel 400.

In another mode of operation of the embodiment the pawl 416 may be rotated from its vertical position to a position where the end of the rod 428 drops into a notch 440 in the cam 422. In this position the rod 4128 moves downwardly to permit the relay armature 72 to effectively Lengage the brake disc 68. When the knob 404 is rotated in either direction, the spring 406 is charged. While the knob is held in twisted position, it is moved inwardly momentarily to close the starting switch 354 for releasing the relay armature 72 from the brake disc 68 to commence tuning movement of the shaft 401 by the spring 406. The tuning is stopped on a signal when an impulse from the receiver releases the' relayarmature as v previously deago/1,676

. 13 scribed. Thus the Ireceiver may be manually tuned in either direction to the next adjacent station having sufficient strength to operate the control relay 70.,

In another mode of operation of the embodiment the pawl 416 is rotated to engage with the ratchet wheel 414. The spring 406 may then be charged to a considerable extent by winding theknob 404 by successive twists. The =spring may be wound in either direction depending upon whether the pawl is positioned to restrain clockwise or counterclockwise rotation of the ratchet wheel 414. When the spring is charged, the knob 404 may lbe moved inwardly momentarily to close the starting switch 354 and thereby to initiate movement of the tuning shaft 401 by the spring 406.

In some cases the shaft 401 for varying the tuning means 399 may be continuously rotatable. This may be the case when the tuning means comprises straight-line capacitance variable capacitors. Continuous rotation of the tuning means in a receiver having such capacitors varies the tuning across the entire tuning range alternately in opposite directions. A scale may be employed with graduations extending over a complete 360 of angular motion. If, for instance, a variable condenser is employed which can rotate only 180, a corresponding scale or dial may be used. When the tuning shaft 401 is continuously rotatable, the knob 404 may be wound to charge the spring 406 to an extent sufiicient to vary the tuning throughout several traverses across the tuning range. Thus Winding or recharging is required less frequently.

Figure 7 illustrates a modified form of the sig-nal tuned radio receiver shown in Figures 3 and 4. The modification of Figure 7 permits manual tuning at any time during signal tuning without the operation of any disconnecting member such as the pin 382 in Figure 3. Moreover signal tuning can be resumed after manual tuning without requiring any separate operation other than the tuning operation itself to effect the change.

In Figure 7 the tuning means 374 of the receiver has a rotatable control shaft 450 which corresponds generally with the shaft 370 shown in Figure 3. A knob 452 is fixed to the shaft 450. A spring 454, coiled around the shaft 450, has its opposite ends fixed to the shaft and to a stationary portion of the tuning means 374 respectively. The dial indicator 378 may be secured to the knob 452. For greater accuracy of manual tuning the knob 452 may be made larger. If desired a tuning scale may be marked on the knob and a stationary index provided.

A gear 456 has a hub 458 which is rotatably mounted on a stem 460 formed on the rear of the knob 452. A coil spring 462 is compressed between the gear 456 and a collar 464 fixed to the rear end of the stern. The spring urges the gear into engagement with a flange 466 on the knob 452. In the modification of Figure 7 the gear 360 and the pinion 364 of Figure 3 are fixed together, for instance, by staking the gear 360 directly to one end of the pinion 364. The ratchet 362 is omitted. The push button 396 for operating the starting switch may be mounted on the panel of the receiver. Other details of the receiver of Figure 7 may be the same as the embodiment of Figures 3 and 4. The gear 458, which replaces the gear 366 of Figure 3, may mesh with the pinion 364. 'I'he compression of the spring 462 may be such that when the armature brake 72 is applied by the spring 74 the friction of the slip joint will be sufficient to hold the shaft 450 in any position to which it is turned against the maximum torque of the spring 454. However, this friction should be insufficient to cause the slippage of the armature brake 72 when it is applied and the knob 452 is turned manually.

For signal tuning, the operation of the receiver illustrated in Figure 7 is similar to the operation of the embodiment of Figures 3 and 4. To minimize variation of spring torque over the entire tuning range, the spring 454 is given several turns so that its initial i4 or minimum tension is large compared with the change in tension from one end to the other of the tuning range. The spring 454 tends to rotate the tuning shaft 450 in one direction which may be counterclockwise as viewed from the front of the receiver. The tension on the spring 454 is increased by manually rotating the knob 452 in the opposite direction. When the spring 454 is being manually charged the gear 456 is not rotated ybecause the frictional drive between the gear and the flange 466 on the knob slips. Consequently the relay armature 72 may remain in contact with the brake disc 68 during charging .ofthe spring.

When the spring 454 rotates the shaft 450 during signal tuning, the gear 456 turns with the knob 452 because the spring 462 is strong enough to provide sufficient friction between the gear and the flange 466 to prevent slippage of the gear. The gear 456 drives the stopping member 68 and the wind vane 69 until the stopping member 68 is stopped by the relay armature 72. The accuracy of the tuning is not affected by the frictional connection between the gear 456 and the knob 452 because the spring 462 is strong enough to prevent slipping when the tuning is stopped on a signal. Signal tuning is started by tapping the push button 396 as in the embodiment of Figures 3 and 4.

For manual tuning, the knob 452 is turned to rotate the tuning shaft 450 to the desired position. When the knob 452 is turned in either direction to charge the spring 454 or to relieve tension on the spring, the knob slips with respect to the gear 456. Thus manual tuning may be accomplished although the relay armature 72 remains in contact with the brake disc 68 and holds -the gear train stationary. The .strength of the spring 462 is such that a moderate amount of manual effort is sufficient to produce slipping between the knob 452 and the gear 456 so that the gear may remain stationary While the knob is rotated.

The receiver illustrated in Figure 7 has the advantage that either signal tuning or manual tuning can be accomplished without operating any changeover control. The receiver is manually tuned by merely rotating the knob 452 to the desired position. During manual tuning, the contacts operated by the relay 70 remain in their listening position. For signal tuning the spring is charged by rotating the knob manually, and then signals are tuned in by tapping the push button 396.

While I have shown and described several preferred embodiments of my invention, it will be apparent that numerous Variations and modifications thereof may be made without departing from the underlying principles of the invention. I therefore desire, by the following claim, to include within the scope of the invention all such variations and modifications by which substantially the results of my invention may be obtained through the use of substantially the same or equivalent means.

I claim:

In a signal tuned radio receiver having a variable tuner, a high frequency amplifier, a detector for selectively producing stopping and listening signals and an audio frequency amplifier, means for effecting signal tuned operation of said receiver including potential energy storage means connected to said tuner for varying said tuner, manually movable means connected to the tuner for charging said energy storage means and for moving said variable tuner from one end of its frequency range to the other by a single continuous manual movement of said movable means, solenoid brake means for stopping said variable tuner, manually controlled switching means connected to the solenoid brake means to control the same for starting variation of said tuner, means including said detector for deriving a stopping signal in response to a signal tuned in by said tuner including a high frequency transformer having a primary coupled to the said high frequency amplifier and a first tuned secondary coupled to said detector, a restraining volt- 15 age rectifier coupled to said primary and to the detector circuit to delay the application of the stopping pulse, means coupling the output of said detector to the input of said audio frequency amplifier, relay means coupled to the output of said audio frequency amplifier and operatively connected to said solenoid brake means, and means operated by said relay means to cause said restraining voltage rectifier to limit the frequency response of said detector during tuning and to render said restraining voltage rectifier inelective during listening, whereby the receiver will be automatically indexed by one phase of operation and good signal tuned reception obtained for a second phase with minimum extra apparatus provided by utilization fratusand-manual energy.

Y References Cited in the vfiile of patentv l UNITED sTATEsPTNTS v Van Loon Jan. v24, 7 Jackson "Feb. 11, Gierwiatowski 'Jan. 10, OBrien Sept. 25, Colgan-i; Goodrich May 19,

of normal receiver appa- 

